Communication supporting method and apparatus using non-access stratum protocol in mobile telecommunication system

ABSTRACT

A method and apparatus for supporting Non-Access Stratum (NAS) communication between a User Equipment (UE) and a Mobility Management Entity (MME) efficiently by addressing the signaling problems occurring between the UE and the MME in a situation where it is necessary for a network node to identify the UE and acquire UE information, if there is any, from another network node to which the UE has been attached, are provided. The method for communication between the UE and network based on the NAS protocol messages and operations is implemented with the involvement a UE, an MME, and an old MME or an old Serving General Packet Radio Service (GPRS) Support Node (SGSN) to which the UE has been attached before so as to facilitate discovering a best node using the UE information acquired from the old MME or old SGSN during the communication between the UE and the network, resulting in a reduction of a communication delay between the UE and network and an improvement of communication efficiency.

PRIORITY

This is a continuation application of U.S. patent application Ser. No.14/507,012, filed on Oct. 6, 2014, which is a continuation of U.S.patent application Ser. No. 13/228,713, filed on Sep. 9, 2011, whichissued as U.S. Pat. No. 8,855,051 on Oct. 7, 2014, and which claimed thebenefit under 35 U.S.C. §119(a) of a Korean patent application filed onSep. 9, 2010 in the Korean Intellectual Property Office and assignedSerial number 10-2010-0088232, the entire disclosure of each of which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication system. Moreparticularly, the present invention relates to a method and apparatusfor supporting Non-Access Stratum (NAS) communication between a UserEquipment (UE) and a Mobility Management Entity (MME) efficiently byaddressing the signaling problems occurring between the UE and MME in asituation where it is necessary for a network node to identify the UEand acquire UE information, if there is any, from another network nodeto which the UE have been attached after a movement between twodifferent Radio Access Technologies (RATs) such as Evolved UniversalTerrestrial Radio Access Network (EUTRAN) and Universal TerrestrialRadio Access Network (UTRAN) or Global System for Mobile Communications(GSM)/Enhanced Data Rates for GSM Evolution (EDGE) Radio Access Network(GERAN).

2. Description of the Related Art

As one of the representative mobile communication standardorganizations, the 3^(rd) Generation Partnership Project (3GPP) hasdefined Evolved Packet System (EPS) with the introduction of MME.

The NAS protocols for the 3GPP 3G system have been revised in order tomeet the requirements of high-speed data transmission in the nextgeneration mobile communication system. The revision also has includedbackward compatibility to the 2G and 3G networks of 3GPP. In detail,when attaching to a network or updating a tracking area, the UEidentifies the network node which it has accessed before using the nodeidentity information of the UE identifier.

In a carrier network of the related art, however, the network isconfigured using even the bit information indicating network nodeidentity information, and thus there is no room to distinguish betweenthe legacy network mobility management node and the MME introduced forsupporting the EUTRAN, resulting in a node identification failureproblem. There is therefore a need of a method for improvingcommunication service quality by minimizing processing delay with theprovision of the information for the UE to discover the network node towhich the UE has attached before and the acquisition of the UEinformation based on the provided information in the communicationbetween the UE and the network through modification of the NAS protocolor a certain procedure of the UE or the mobility management node.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a communication method and system for supportingNon-Access Stratum (NAS) communication between a User Equipment (UE) anda network node efficiently in an evolved mobile communication systemincluding 3^(rd) Generation Partnership Project (3GPP) Evolved PacketSystem (EPS) supporting Access Stratum (AS) and NAS protocols on layer2, especially when the UE in idle mode moves or connects to a network orupdates the tracking area or performs handover between different RadioAccess Technologies (RAT) including Evolved Universal Terrestrial RadioAccess Network (EUTRAN) and Universal Terrestrial Radio Access Network(UTRAN) or Global System for Mobile Communications (GSM)/Enhanced DataRates for GSM Evolution (EDGE) Radio Access Network (GERAN)(UTRAN/GERAN).

Another aspect of the present invention is to provide a communicationmethod and system that is capable of supporting NAS authentication andNAS communication between a UE and a network entity such as a MobilityManagement Entity (MME) without a processing delay by specifying theoperations of the UE, MME, and Serving General Packet Radio Service(GPRS) Support Node (SGSN) in the NAS protocol during the roaming of theUE between different technology-based networks including GERAN, UTRAN,EUTRAN, and other equivalent access networks.

The present invention relates to a method and system for facilitating aUE to discover a best node during or in attempt of communication with anetwork node using the NAS protocols, and the method for communicationbetween the UE and network based on the NAS protocol messages andoperations according to the present invention is implemented with theinvolvement a UE, an MME, and an old MME or old SGSN to which the UE haspreviously attached so as to facilitate discovering the best node usingthe UE information acquired from the old MME or old SGSN during thecommunication between the UE and the network, resulting in a reductionof communication delay between the UE and network and an improvement ofcommunication efficiency.

As aforementioned, the present invention is capable of maintaining thecommunication between UE and network during the handover between twodifferent RATs such as EUTRAN and UTRAN/GERAN, resulting in reduction ofcommunication delay.

In accordance with an aspect of the present invention, a communicationsupport method of an MME in a mobile communication system is provided.The method includes receiving a Packet-Temporary Mobile SubscriberIdentity (P-TMSI) signature from a UE in an access request, anddetermining an old network node which the UE has accessed previously byanalyzing the P-TMSI.

In accordance with another aspect of the present invention, acommunication support apparatus of an MME in a mobile communicationsystem is provided. The apparatus includes a communication unit whichreceives a P-TMSI signature from a UE in an access request, and adetermination unit which determines an old network node which the UE hasaccessed previously by analyzing the P-TMSI.

In accordance with another aspect of the present invention, acommunication support method of a UE in a mobile communication system isprovided. The method includes transmitting a P-TMSI signature to an MMEin an access request, and receiving an access response from the MME inresponse to the access request, wherein the MME analyzes the P-TMSI todetermine an old network node which the UE has accessed previously.

In accordance with still another aspect of the present invention, acommunication support apparatus of a UE in a mobile communication systemis provided. The apparatus includes a communication unit which isresponsible for communication with an MME, and a control unit whichtransmits a P-TMSI signature to the MME in an access request andreceives an access response from the MME in response to the accessrequest, wherein the MME analyzes the P-TMSI to determine an old networknode to which the UE has accessed previously.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating communication environment ofthe mobile communication system according to an exemplary embodiment ofthe present invention;

FIG. 2 is a signaling diagram illustrating a network attachmentprocedure of a User Equipment (UE) according to an exemplary embodimentof the present invention;

FIG. 3 is a signaling diagram illustrating a tracking area updateprocedure of a UE according to an exemplary embodiment of the presentinvention;

FIG. 4 is a signaling diagram illustrating a network attachmentprocedure of a UE according to another exemplary embodiment of thepresent invention;

FIG. 5 is a signaling diagram illustrating a tracking area updateprocedure of a UE according to another exemplary embodiment of thepresent invention;

FIG. 6 is a flowchart illustrating operations of a Mobility ManagementEntity (MME) for supporting communication between a UE and a networknode according to an exemplary embodiment of the present invention;

FIG. 7 is a flowchart illustrating operations of a UE for supportingcommunication between the UE and a network node according to anexemplary embodiment of the present invention; and

FIG. 8 is a flowchart illustrating operations of an MME for supportingcommunication between a UE and a network node according to anotherexemplary embodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The subject matter of the present invention is to provide a method forreducing the delay of Non-Access Stratum (NAS) communication between aUser Equipment (UE) and a Mobility Management Entity (MME) by optimizingthe operations of the UE, MME, and Serving General Packet Radio Service(GPRS) Support Node (SGSN) in the NAS signaling. Although thedescription is directed to the 3^(rd) Generation Partnership Project(3GPP)-based system including Evolved Packet System (EPS), UniversalTerrestrial Radio Access Network (UTRAN), and Global System for MobileCommunications (GSM)/Enhanced Data Rates for GSM Evolution (EDGE) RadioAccess Network (GERAN), the present invention can be applied to othertypes of communication systems using NAS.

In the exemplary embodiment of FIG. 1, the present invention proposes acommunication method between a UE and an MME and operations thereofbased on the NAS protocol during the movement of the UE betweendifferent Radio Access Technologies (RAT) including Evolved UniversalTerrestrial Radio Access Network (EUTRAN) and Universal TerrestrialRadio Access Network (UTRAN), and it will be obvious to those skilled inthe art that the disclosed communication method can be applied to othermobile communication systems implemented based on similar or differentprotocols but operating similarly in similar technological backgroundand channel format with minor changes and modifications withoutdeparting from the scope of the present invention.

FIG. 1 is a schematic diagram illustrating a communication environmentof a mobile communication system according to an exemplary embodiment ofthe present invention. The description is directed to an exemplary 3GPPEPS system. Although the description is directed to the case where theUE connects to a EUTRAN and then moves to another RAT network orconnects to an RAT network and then moves to the EUTRAN, the presentinvention can be applied to other mobile communication systems operatingin a similar manner.

Referring to FIG. 1, the base stations (referred to as Evolved Node BaseStation, E Node B, and eNB, or Radio Network Controller (RNC)) 112 and133 are responsible for establishing radio links to communicate with theUE 110 within the cell as the service coverage thereof. The UE 110 is aterminal that connects to a packet data network such as the Internet viaa Serving Gateway (hereinafter, referred to as Serving GW or S-GW) 116.In the following description, the Packet Data Network Gateway(hereinafter, referred to as PDN GW) 118 as a significant network entityof the packet data network is responsible for the functions of HomeAgent HA. The Mobility Management Entity/Serving GPRS Support Node(MME/SGSN) 135 is responsible for management of mobility, location, andregistration of the UE. In order to manage the authenticationinformation of the user or UE, the Home Subscriber Server (HSS) 121 isconnected to the MME 114 and MME/SGSN 135 via an interface.

The eNB/RNC 133, SGW 116, and MME/SGSN 135 are connected via data pathswith the interface for managing the mobility of UE. The UE 110 andMME/SGSN 135 have an NAS protocol stack to communicate each other forthe mobility management and session management. In the describedexemplary embodiment, the description is directed to the situation inwhich the UE 100 connected to an old network (or source network) movesto connect to a new network or updates location. The source network canbe one of various RATs including EUTRAN, UTRAN, and GERAN, and it isassumed that the UE moves from the source network to EUTRAN as the newnetwork (or target network). If it moves to the target network, the UE110 connects to the eNB 112 so as to be served by the eNB 112, MME 114,and HSS 121. The MME 114 of the new network and the MME/SGSN 135 of theold network are connected with each other so as to exchange theinformation necessary. A description is made of the operations of the UE110 and MME 114 operating based on the NAS protocol in theabove-structured network with reference to FIGS. 2 to 8. In the mobilecommunication system according to an exemplary embodiment of the presentinvention, when a request message is received from the UE, the networknode analyzes the request message to check the old network node to whichthe UE has been attached. The new network node requests the old networknode for the information related to the UE. When the UE information isreceived from the old network node, the new network node sends aresponse message to the UE using the acquired UE information.

In the mobile communication system of the present invention, the UEconfigures the request message. The UE configures the request message inorder for the network node to analyze the request message to check theold network node. The UE sends the request message to the network node.Afterward, the UE receives the response message transmitted by thenetwork node in response to the request node.

Here, the request message includes the connection request message forconnection to the network node and the update request message forupdating the UE location. The new network node can be an MME, and theold network node can be a SGSN or MME.

FIG. 2 is a signaling diagram illustrating a network attachmentprocedure of a UE according to an exemplary embodiment of the presentinvention.

Referring to FIG. 2, the UE 110 requests attachment to the network atstep 201. At this time, the UE sends an access request message, i.e.,Attach Request message, including UE identity information which isreferred to as Packet-Temporary Mobile Subscriber Identity (P-TMSI)signature. The P-TMSI signature is the information to be used in theattempt of attachment to a network since the UE 110 has successfullyconnected to an SGSN. The Attach Request message is delivered to the MME114 via the eNB 112 at step 203.

If it is determined that the UE 110 has accessed the old MME/SGSN 135,the new MME 114 determines the type of the old network node at step 205.The old network node type is determined by referencing the MostSignificant Bit (MSB) of the Local Area Code (LAC) or MME Group Identity(MMEGI) in the Globally Unique Temporary Identity (GUTI) of the UE 110.Once the old network node type is determined (if the MSB is set to 1,the old network is determined to be EUTRAN, and otherwise the oldnetwork is determined to be UTRAN/GERAN), the UE discovers the MME orSGSN in the corresponding network. In the case that the MSB is set to 1for the UTRAN/GERAN (by some mobile carriers), if the Attach Requestmessage transmitted by the UE 110 includes a valid P-TMSI signature, itcan be determined that the UE 110 has accessed the GERAN/UTRANpreviously.

Next, the new MME 114 requests the MME/SGSN 135, as the old servingnetwork of the UE 110, for the International Mobile Subscriber Identity(IMSI) and Mobility Management (MM) context at step 207. The new MME 114receives the UE information from the old MME/SGSN 135 at step 209. Next,the authentication and security process is performed at step 211 andthen the bearer creation process is performed at step 213. Next, the newMME 114 sends an Attach Accept message to the new eNB 112 at step 215,and the new eNB 112 forwards the Attach Accept message to the UE 110 atstep 217 so as to complete the attachment procedure.

FIG. 3 is a signaling diagram illustrating a tracking area updateprocedure of UE according to an exemplary embodiment of the presentinvention.

Referring to FIG. 3, the UE 110 sends a Tracking Area Update (TAU)Request message to the network through new eNB 112 at step 301. The TAURequest message includes a P-TMSI signature as UE identity informationand a Cipher Key Sequence Number (CKSN) for referencing a cipher keywhen the UE 110 has accessed a GERAN/UTRAN previously. If there exists avalid CKSN and P-TMSI signature, this means that the UE has successfullyconnected to an SGSN previously and stored the information for use inthe connection or location registration update process afterward. TheTAU Request message transmitted by the UE 110 is delivered to the MME114 via the eNB 112 at step 303.

In case that the UE has accessed the MME/SGSN 135 previously, the MME114 determines the type of the old network node at step 305. The oldnetwork node type is determined by referencing the MSB of the LAC orMMEGI in the GUTI of the UE 110. Once the old network node type isdetermined (if the MSB is set to 1, the old network is determined to beEUTRAN, and otherwise the old network is determined to be UTRAN/GERAN),the UE discovers the MME or SGSN in the corresponding network. In casethat the MSB is set to 1 for the UTRAN/GERAN (by some mobile carriers),if the Attach Request message transmitted by the UE 110 includes a validP-TMSI signature, it can be determined that the UE 110 has accessed theGERAN/UTRAN previously.

Next, the new MME 114 requests the MME/SGSN 135, as the old servingnetwork of the UE 110, for the IMSI and MM context at step 307. The newMME 114 receives the UE information from the old MME/SGSN 135 at step309. Next, the authentication and security process is performed at step311 and then the bearer update process for updating Serving Gateway andUE location information is performed at step 315. The new MME 114 sendsa Context Acknowledge message to the old MME/SGSN 135 for acknowledgmentof the receipt of the UE information at step 313. After the bearerupdate at step 315, the new MME 114 sends a TAU Accept message to the UE110 at step 317 so as to complete the tracking area update procedure.

According to an exemplary embodiment of the present invention, if anAttach Request or a tracking area update request message is receivedfrom the UE, the network node checks the MSB of the MMEGI or the LAC ofthe GUTI of the UE in the request message. If the MSB is set to 0, thismeans that the old network node is SGSN. Otherwise if the MSB is set to1, the new network node determines whether the request message includesat least one of a P-TMSI signature and a CKSN. If the request messageincludes at least one of the P-TMSI signature and the CKSN, this meansthat the old network node is SGSN. Otherwise if the request messageincludes neither the P-TMSI signature nor the CKSN, this means that theold network node is MME. Afterward, the new network node requests theold network node for the UE information and sends a response message tothe UE using the UE information received from the old network node.

FIG. 4 is a signaling diagram illustrating a network attachmentprocedure of UE according to another exemplary embodiment of the presentinvention.

Referring to FIG. 4, the UE 110 requests attachment to the network atstep 401. The Attach Request message transmitted by the UE includes thecapability information on whether the UE 110 is capable ofdiscriminating between the identifier assigned as the result of theconnection to an MME and the identifier created based on the P-TMSI orRouting Area Identity (RAI). The capability information can betransmitted in a parameter, i.e., a UE network capability InformationElement (IE), or in other ways. The UE 110 can transmit the AttachRequest message including the information indicating whether theidentifier is assigned as the result of attachment to MME or createdfrom the P-TMSI and/or RAI. The identifier creation information can betransmitted by means of a type of identity (identification type or IDtype) or other IE or discriminate between LAC and MMEGI. The AttachRequest message transmitted by the UE 110 is delivered to the MME 114via the eNB 112 at step 403.

If it is determined that the UE 110 has accessed the old MME/SGSN 135,the new MME 114 determines the type of the old network node at step 405.The old network node type is determined by referencing the MSB of theLAC or MMEGI in the GUTI of the UE 110. Once the old network node typeis determined (if the MSB is set to 1, the old network is determined tobe EUTRAN, and otherwise the old network is determined to beUTRAN/GERAN), the UE discovers the MME or SGSN in the correspondingnetwork. In case that the MSB is set to 1 for the UTRAN/GERAN (by somemobile carriers), if the Attach Request message transmitted by the UE110 includes capability information, this means that the UE 110 has thecapability of transmitting identification type along with the GUTI.Accordingly, the MME 114 references an identification type field or theIE related to identification type to determine whether the old networknode to which the UE has attached is GERAN/UTRAN or EUTRAN.

Next, the new MME 114 requests the MME/SGSN 135, as the old servingnetwork of the UE 110, for the IMSI and MM context as the UE informationat step 407. The new MME 114 receives the UE information from the oldMME/SGSN 135 at step 409. Next, the authentication and security processis performed at step 411 and the bearer creation process is performed atstep 413. Next, the new MME 114 sends an Attach Accept message to thenew eNB 112 at step 415, and the new eNB 112 forwards the Attach Acceptmessage to the UE 110 at step 417 so as to complete the attachmentprocedure.

FIG. 5 is a signaling diagram illustrating a tracking area updateprocedure of a UE according to another exemplary embodiment of thepresent invention.

Referring to FIG. 5, the UE 110 sends a TAU Request message to thenetwork through new eNB 112 at step 501. The Attach Request messagetransmitted by the UE includes the capability information on whether theUE 110 is capable of discriminating between the identifier assigned asthe result of the connection to an MME and the identifier created basedon the P-TMSI or RAI. The capability information can be transmitted in aparameter, i.e., a UE network capability IE, or in other ways. The UE110 can transmit the Attach Request message including the informationindicating whether the identifier is assigned as the result ofattachment to MME or created from the P-TMSI and/or RAI. The identifiercreation information can be transmitted by means of a type of identity(identification type or ID type) or other IE or discriminate between LACand MMEGI. The Attach Request message transmitted by the UE 110 isdelivered to the MME 114 via the eNB 112 at step 503. If it isdetermined that the UE 110 has accessed the old MME/SGSN 135, the newMME 114 determines the type of the old network node at step 505. The oldnetwork node type is determined by referencing the MSB of the LAC orMMEGI in the GUTI of the UE 110. Once the old network node type isdetermined (if the MSB is set to 1, the old network is determined to beEUTRAN, and otherwise the old network is determined to be UTRAN/GERAN),the UE discovers the MME or SGSN in the corresponding network. In casethat the MSB is set to 1 for the UTRAN/GERAN (by some mobile carriers),if the Attach Request message transmitted by the UE 110 includescapability information, this means that the UE 110 has the capability oftransmitting identification type along with the GUTI. Accordingly, theMME 114 references an identification type field or the IE related toidentification type to determine whether the old network node to whichthe UE has attached is GERAN/UTRAN or EUTRAN.

Next, the new MME 114 requests the MME/SGSN 135, as the old servingnetwork of the UE 110, for the IMSI and MM context as the UE informationat step 507. The new MME 114 receives the UE information from the oldMME/SGSN 135 at step 509. Next, the authentication and security processis performed at step 511 and the bearer modification process forupdating the serving gateway and UE location information is performed atstep 515. The new MME sends a Context Acknowledge message to the oldMME/SGSN 135 for acknowledgment of the receipt of the UE information atstep 513. After the bearer modification at step 515, the new MME 114sends a TAU Accept message to the UE 110 at step 517 so as to completethe tracking area update procedure.

According to this exemplary embodiment of the present invention, the UEconfigures an identification type indicator for discriminating the typesof the temporary identifier of the network node which is transmitted inthe request message such as the Attach Request and Tracking Area UpdateRequest message. The UE transmits the request message to the networknode. Afterward, the UE receives a response message from the networknode in response to the request message.

According to another exemplary embodiment of the present invention, ifthe request message such as Attach Request or Tracking Area UpdateRequest is received from the UE, the network node determines whether therequest message includes the identification type indicator forindicating the type of the old network node based on the temporaryidentifier. If the request message includes the identification typeindicator, the network node identifies the old network node as one ofSGSN and MME. At this time, the network node analyzes the identificationtype indicator related to the temporary identifier corresponding to theold network node to determine the old network node as one of SGSN andMME. Afterward, the network nod receives the UE information from the oldnetwork node and sends the response message to the UE using the UEinformation.

FIG. 6 is a flowchart illustrating operations of an MME for supportingcommunication between a UE and a network node according to an exemplaryembodiment of the present invention.

Referring to FIG. 6, the MME 114 receives the Attach Request/TAU Requestmessage transmitted by the UE 110 at step 701. Upon receipt of therequest message, the MME 114 checks the EPS mobile identity IE in therequest message at step 703. If the MSB of LAC/MMEGI is determined to beset to 0 at step 721, this means that the old network node to which theUE 110 has been attached is SGSN, and thus the MME 114 discovers thecorresponding one among a plurality of SGSNs to request for UEinformation at step 723.

If the MSB of LAC/MEGI is determined to be set to 1 at step 711, thismeans that the old network node to which the UE 110 has been attached isMME or SGSN, and thus the MME 114 determines whether the Attach Requestmessage transmitted by the UE 110 includes a valid P-TMSI signature orthe TAU Request message transmitted by the UE 110 includes at least oneof a CKSN or a P-TMSI signature at step 713. If it is determined thatthe request message includes a valid CKSN or a P-TMSI signature, thismeans that the old network node to which the UE has been attachedpreviously is SGSN, and thus the MME 114 discovers the targeted one ofSGSNs to request for the UE information at step 715. Otherwise, if it isdetermined that the request message includes neither a valid P-TMSIsignature nor a CKSN, this means that the old network node to which theUE has been attached previously is MME, and thus the MME 114 discoversthe targeted one among MMEs to request for the UE information at step717.

According to an exemplary embodiment of the present invention, the MMEincludes a communication unit, a determination unit, and a control unit.

The communication unit is responsible for communication with the UE. Thecommunication unit can receive the access request message from the UE.Here, the access request message can be one of an Attach Request or aTracking Area Update Request.

The determination unit analyzes the access request message transmittedby the UE to determine the type of the old network node. Here, thedetermination unit analyzes the P-TMSI signature to determine the typeof the old network node. The determination unit can include a judgingmodule and an identification module. The determination unit analyzes theP-TMSI signature of the access request message. The identificationmodule judges the old network node as one of MME and SGSN according tothe analysis result of P-TMSI signature.

The control unit requests the old network node for the UE information.Upon receipt of the UE information, the control unit controls such thatthe network node sends the response message to the UE using the acquiredUE information.

According to an exemplary embodiment of the present invention, the UEincludes a communication unit and a control unit. The control unitcontrols to transmit an access request message to the MME. Here, thecontrol unit controls such that the P-TMSI signature is transmitted inthe access request message. The access request message can be one of anAttach Request and a Tracking Area Update Request of the UE. Thecommunication unit is responsible for communication with the MME. Atthis time, the communication unit receives an Access Response messagefrom the MME in response to the Access Request message.

FIG. 7 is a flowchart illustrating operations of a UE for supportingcommunication between the UE and a network node according to anexemplary embodiment of the present invention.

Referring to FIG. 7, the UE 110 determines whether the technologyrelease version (hereinafter, referred to as rel) is rel_(—)8 or postrel_(—)8, i.e., rel_(—)9 or rel_(—)10, at step 801. The operations canbe defined differently according to the technology release version. Incase of rel_(—)8, the UE 110 configures the Attach/TAU Request messagewith UE network capability or other indication information elementindicating GUTI/mapped GUTI or without identifier at step 821 andtransmits the Attach/TAU Request message to the network node at step819.

In case of post rel_(—)8 (i.e., rel_(—)9 or rel_(—)10), the UE 110 setsa valid UE network capability at step 811 and determines whether to usethe GUTI or mapped GUTI as the identification type information, based onthe identification type indication capability of the UE, at step 813. Ifit is determined to use GUTI, the UE 110 configures the Attach/TAURequest message with the identification type field or identificationtype-related IE set to indicate GUTI at step 815, and otherwise to usemapped GUTI, configures the Attach/TAU Request message with theidentification type field or identity-related IE set to indicate mappedGUTI at step 817. Next, the UE 110 sends the Attach/TAU Request messageto the network at step 819.

According to an exemplary embodiment of the present invention the UEincludes a control unit and a communication unit. The control unitconfigures the request message with the identification type indicatorfor notifying the network node of the type of the old network nodecorresponding to the temporary identifier. The control unit configuresthe request message with the identification type information of thetemporary identifier corresponding to the old network node. Thecommunication unit transmits the request message to the network nodeunder the control of the control unit. The communication unit alsoreceives a response message from the network node in response to therequest message.

FIG. 8 is a flowchart illustrating operations of an MME for supportingcommunication between a UE and a network node according to anotherexemplary embodiment of the present invention.

Referring to FIG. 8, the MME 114 receives the Attach/TAU Request messagetransmitted by the UE 110 at step 901. Upon receipt of the Attach/TAURequest message, the MME 114 analyzes the Attach/TAU Request message tocheck the UE network capability at step 903. If the Attach Requestmessage or the TAU Request message includes the identification typeindication capability-related information configured, this means thatthe UE 110 has the identification type indication capability intransmitting GUTI-related information. In this case, the MME 114 checksthe identification type field or identification type-related IE of therequest message to determine whether the old network node to which theUE has been attached previously is GERAN/UTRAN or EUTRAN at step 911. Ifthe identification type-related information is determined to be GUTI,this means that the old network node is MME, and thus the MME 114discovers the targeted one among the MMEs to request for the UEinformation at step 917. Otherwise if the identification type-relatedinformation is the mapped GUTI, this means that the old network node isSGSN, and thus the MME 114 discovers the targeted one among the SGSNs torequest for the UE information at step 913.

Returning to step 903, if the Attach Request message or the TAU Requestmessage does not include identification typediscrimination-capability-related information, this means that the UEhas no identity indication capability, and thus the MME 114 refers atstep 921 to the MSB of the MMEGI or LAC in the GUTI or mapped GUTI so asto select one of the SGSNs as the old network node if the MSB isdetermined to be set to 0 and one of the MMEs (or one of SGSNs accordingto the network configuration of the carrier) as the old network node ifthe MSB is determined to be set to 1. In this case, the MME 114 candetermine the SGSN to which the UE 110 has attached previously among aplurality of SGSNs based on the additional information such as a CKSN ora P-TMSI signature.

According to an exemplary embodiment of the present invention, the MMEincludes a communication unit, a determination unit, and a control unit.

The communication unit is responsible for communication with the UE. Thecommunication unit can receive the Access Request message transmitted bythe UE. Here, the Access Request message can be one of Attach Requestand Tracking Area Update Request of the UE.

The determination unit analyzes the access request message transmittedby the UE to determine the type of the old network node. Thedetermination unit includes a judging module and an identificationmodule. The judging unit judges whether the identification typeindicator for discriminating the type of the old network is configuredby the UE in association with the temporary identifier of the UE. If noidentification type indicator is configured, the identification moduledetermines the old network node to be one of the SGSNs and MMEs. At thistime, the identification module analyzes the information related to theidentification type of the temporary identifier corresponding to the oldnetwork node in the request message to identify whether the old networknode is an SGSN or an MME.

The control unit requests the old network node for the UE information.If the UE information is received from the old network node, the controlunit sends the response message to the UE using the acquired UEinformation.

In order to support communication between the UE and the MME asdescribed above with reference to FIGS. 2 to 8, it is necessary tosupport the IE in the messages as shown in Table 1. Table 1 shows the IEindicating whether the UE has the capability of informing the networknode of the identification type in the message. According to anexemplary embodiment of the present invention, the identification typeindication capability is configured in octet 7.

TABLE 1 8 7 6 5 4 3 2 1 UE network capability IEI octet 1 Length of UEnetwork capability contents octet 2 EEA0 128-EEA1 128-EEA2 EEA3 EEA4EEA5 EEA6 EEA7 octet 3 EIA0 128-EIA1 128-EIA2 EIA3 EIA4 EIA5 EIA6 EIA7octet 4 UEA0 UEA1 UEA2 UEA3 UEA4 UEA5 UEA6 UEA7 octet 5* UCS2 UIA1 UIA2UIA3 UIA4 UIA5 UIA6 UIA7 octet 6* 0 0 0 ID LPP LCS 1xSR NF octet 7*spare spare spare TYPE VCC indi- cation 0 0 0 0 0 0 0 0 octet 8*- Spare15* Identification type indication capability (octet 7, bit 5) 0Identification type indication mechanisms not supported 1 Identificationtype indication mechanisms supported

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

The present invention achieves the following effects from the abovedescribed representative exemplary embodiments.

The present invention provides a method and system for addressing theproblem of delay in NAS protocol-based communication due to a failure ofacquiring UE information from a valid network node, especially in asituation where the UE attempts network attachment or Tracking AreaUpdate during the movement between different RATs including EUTRAN andGERAN/UTRAN. The method and system using the NAS protocol message andoperations of the UE and MME that are defined according to the presentinvention are advantageous to facilitate communication between the UEand network node.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method by a network node in a mobilecommunication system, the method comprising: receiving a first requestmessage from a terminal, the first request message being an attachrequest message or a tracking area update request message; identifyingwhether the first request message includes a packet-temporary mobilesubscriber identity (P-TMSI) signature assigned to the terminal from anold network node; identifying a type of the old network node as aserving general packet radio service support node (SGSN) if the P-TMSIsignature is included in the first request message and the type of theold network node as a mobility management entity (MME) if the P-TMSIsignature is not included in the first request message; and transmittinga second request message to the old network node based on the identifiedtype of the old network node.
 2. The method of claim 1, wherein thesecond request message is transmitted to the old network node to requestan international mobile subscriber identity (IMSI) of the terminal. 3.The method of claim 1, further comprising: receiving a first responsemessage including at least one of IMSI of the terminal and mobilitymanagement context from the old network node in response to the secondrequest message.
 4. The method of claim 1, further comprising:transmitting a second response message to the terminal, the secondmessage being an attach accept message or a tracking area update acceptmessage.
 5. The method of claim 3, further comprising: transmitting athird request message for creating a bearer to a serving gateway basedon at least one of the first request message and the first responsemessage.
 6. An apparatus of a network node in a mobile communicationsystem, the apparatus comprising: a transceiver configured to transmitand receive a signal; and a controller configured to receive, from aterminal, a first request message being an attach request message or atracking area update request message, to identify whether the firstrequest message includes a packet-temporary mobile subscriber identity(P-TMSI) signature assigned to the terminal from an old network node, toidentify a type of the old network node as a serving general packetradio service support node (SGSN) if the P-TMSI signature is included inthe first request message and the type of the old network node as amobility management entity (MME) if the P-TMSI signature is not includedin the first request message, and to transmit a second request messageto the old network node based on the identified type of the old networknode.
 7. The apparatus of the claim 6, wherein the second requestmessage is transmitted to the old network node to request aninternational mobile subscriber identity (IMSI) of the terminal.
 8. Theapparatus of the claim 6, wherein the controller is further configuredto receive a first response message including at least one of IMSI ofthe terminal and mobility management context from the old network nodein response to the second request message.
 9. The apparatus of the claim6, wherein the controller is further configured to transmit a secondresponse message to the terminal, the second message being attach anaccept message or a tracking area update accept message.
 10. Theapparatus of the claim 8, wherein the controller is further configuredto transmit a third request message for creating a bearer to a servinggateway based on at least one of the first request message and the firstresponse message.
 11. A method by a terminal in a mobile communicationsystem, the method comprising: generating a first request message, thefirst request message being an attach request message or a tracking areaupdate request message; and transmitting the first request message to anetwork node, wherein the first request message includes apacket-temporary mobile subscriber identity (P-TMSI) signature assignedto the terminal from an old network node if a type of the old networknode as a serving general packet radio service support node (SGSN), andthe first request message does not include the P-TMSI signature if thetype of the old network node is a mobility management entity (MME). 12.The method of claim 11, wherein the network node transmits a secondrequest message to the old network node to request an internationalmobile subscriber identity (IMSI) of the terminal.
 13. The method ofclaim 11, wherein the network node receives a first response messageincluding at least one of IMSI of the terminal and mobility managementcontext from the old network node in response to the second requestmessage.
 14. The method of claim 11, further comprising: receiving asecond response message from the network node, the second message beingan attach accept message or a tracking area update accept message. 15.The method of claim 13, wherein the network node transmits a thirdrequest message for creating a bearer to a serving gateway based on atleast one of the first request message and the first response message.16. A terminal of a mobile communication system, the terminalcomprising: a transceiver configured to transmit and receive a signal;and a controller configured to generate a first request message, thefirst request message being an attach request message or a tracking areaupdate request message, and to transmit the first request message to anetwork node, wherein the first request message includes apacket-temporary mobile subscriber identity (P-TMSI) signature assignedto the terminal from an old network node if a type of the old networknode as a serving general packet radio service support node (SGSN), andthe first request message does not include the P-TMSI signature if thetype of the old network node is a mobility management entity (MME). 17.The terminal of claim 16, wherein the network node transmits a secondrequest message to the old network node to request an internationalmobile subscriber identity (IMSI) of the terminal.
 18. The terminal ofclaim 16, wherein the network node receives a first response messageincluding at least one of IMSI of the terminal and mobility managementcontext from the old network node in response to the second requestmessage.
 19. The terminal of claim 16, wherein the controller is furtherconfigured to receive a second response message from the network node,the second message being an attach accept message or a tracking areaupdate accept message.
 20. The terminal of claim 16, the network nodetransmits a third request message for creating a bearer to a servinggateway based on at least one of the first request message and the firstresponse message.